Photothermal Imaging of Defects in Metals and Ceramics.
Abstract
Photothermal - or Thermal-Wave - Imaging is a new technique for the characterization and nondestructive evaluation of materials. This report describes developments in the method, theory, and application of thermal-wave imaging techniques. A theory of multilayer films has been developed which has shown that both thermal (and for optical sources) optical-boundary-condition reflections contribute to the temperature field within the specimen and hence affect the ability of thermal-wave imaging methods to determine the depth (or thickness) of buried flaws (or layers). An analysis has been made which shows that thermal barriers affecting heat flow in a heterogeneous material are of two types, one type depending exclusively on thermal properties and the other type depending on both thermal and optical properties. Applications of thermal-wave imaging have included grain-boundary studies in metals, studies of void location and sizing, and closed crack visualization using both thermal and thermoelastic methods. Thermal-wave imaging is a pervasive technique for nondestructive evaluation, encompassing a variety of experimental configurations, each supplying different physical information; three different types of processes are effective in creating thermal images; this technique is suitable for studying the microstructure of a variety of materials; thermoelastic mechanisms are operative in thermal-wave imaging; that momentum processes are ineffective in producing thermal images using particle beam sources. We have developed a new thermal wave imaging technique using an ion-beam as the excitation source.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1986
- Accession Number
- ADA175487
Entities
People
- J. C. Murphy
- L. C. Aamodt
Organizations
- Johns Hopkins University